Wireless communication terminal device, wireless communication base station device and wireless communication method

ABSTRACT

A radio terminal is provided that can provide a flexible transmission power control for an SRS without restrictions due to the transmission power control of a PUSCH, for the purpose of enabling use of an SRS for various purposes in a HetNet CoMP environment. The radio terminal receives a control signal including a transmission power control command (TPC command) to be applied to an aperiodic sounding reference signal (A-SRS), through a physical downlink control channel (PDCCH), updates a transmission power value of the A-SRS using the TPC command, and transmits the A-SRS using the updated transmission power value in accordance with a transmission request included in a control signal indicating assignment of a physical downlink data channel (PDSCH) or assignment of a physical uplink data channel (PUSCH).

TECHNICAL FIELD

The present invention relates to a radio communication terminalapparatus, a radio communication base station apparatus, and a radiocommunication method.

BACKGROUND ART

In LTE (Long Term Evolution) and an evolved version thereof, i.e., LTE-A(LTE-Advanced) formulated in 3GPP (3rd Generation Partnership Project),uplink is provided employing SC-FDMA (Single-Carrier Frequency-DivisionMultiple Access) with a small PAPR (Peak-to-Average Power Ratio) andhigh power usage efficiency in a terminal (for example, see Non-PatentLiterature (hereinafter, abbreviated as NPLs) 1 to 4). In uplink of LTEand LTE-A, scheduling for allocating time and frequency resourcesaccording to the propagation path environment of the terminal, andadaptive control for controlling a coding rate or a modulation schemeare performed. In order to appropriately perform frequency schedulingand adaptive control to enable high throughput, it is indispensable fora base station side to know the propagation path situation of theterminal.

In order to measure the uplink propagation path situation of theterminal, an SRS (Sounding Reference Signal) is used in uplink of LTE(NPL 1). An SRS is a reference signal transmitted with the last SC-FDMAsymbol of an uplink subframe (PUSCH: Physical Uplink Shared Channel)including a plurality of SC-FDMA symbols. A base station can know theuplink situation according to CSI (Channel State Information) calculatedusing the SRS or the reception quality of the SRS.

LTE employs a P-SRS (Periodic-SRS) transmitted periodically at timeindicated by an instruction from a higher layer, such as RRC (RadioResource Control) information. The base station beforehand instructs theterminal on the transmission subframe for an SRS, the period thereof,the power offset for the SRS to be transmitted, the frequency bandwidth,the frequency position, and an orthogonal resource, such as Comb or CS(Cyclic Shift) for orthogonalization to an SRS of another terminal. Theterminal transmits an SRS with the last SC-FDMA symbol in the instructedsubframe. In this way, regardless of the presence or absence oftransmission of data and a control signal in uplink, the base stationcan periodically measure CSI of the terminal.

Meanwhile, uplink packet communication generally has high burstiness. Itis preferable for a base station to be able to measure CSI on anecessary band when needed. Moreover, even when performing no datacommunication in uplink or downlink, a terminal periodically transmitsan SRS and therefore consumes extra power. For this reason, LTE-Aemploys an A-SRS (Aperiodic-SRS) to be transmitted on the basis of atransmission request included in DCI (Downlink Control Information)which is a control signal indicating data assignment in uplink anddownlink. An A-SRS is transmitted only upon request. This can reduceunnecessary power consumption in the terminal, also reduce interferenceto and from another cell and improve the efficiency of SRS resources.

Note that, there has been a discussion on the introduction of aheterogeneous network (HetNet) in which a plurality of base stations(hereinafter referred to as nodes) providing different coverage areasare deployed in a cell in LTE Release 11 (hereinafter referred to asRel. 11), which is a further evolved version of LTE-A. A HetNet enable,for example, reception in a receiving node with a small path loss andoffload for traffic, and therefore enables high throughput. Moreover, aterminal can decrease transmission power for a receiving node with asmall path loss and can therefore reduce power consumption. For thesereasons, in comparison with a non-HetNet involving only a macro node, aHetNet can improve a transmission speed while reducing necessarytransmission power for a terminal.

Moreover, CoMP (Coordinated Multi-Point) in which these nodes transmitand receive a signal in cooperation has also been discussed in Rel. 11HetNet (NPL 4). FIG. 1 illustrates an example of a HetNet CoMP system.HetNet CoMP includes one or more macro base stations (macro nodes), oneor more pico base stations (pico nodes), and one or more terminals. CoMPcan enhance an SNR (Signal-to-Interference plus Noise Power Ratio), forexample, by a plurality of nodes receiving and combining signalstransmitted by a terminal that is located at a cell edge and is stronglyinfluenced by interference. Moreover, nodes can transmit and receive ina coordinated manner. Therefore, optimal nodes can be used independentlyin uplink and downlink. For example, a PDSCH is preferably transmittedby a node maximizing the reception power in a terminal, and a PUSCH ispreferably received by a node minimizing a path loss. Introduction ofCoMP enables communication with different nodes in uplink and downlink.This prevents large differences in the throughput and quality betweenuplink and downlink.

In order to acquire the effect of HetNet CoMP, it is important toappropriately select transmitting/receiving nodes participating incommunication from among nodes distributed geographically, and toappropriately switch between nodes according to a peripheral situationor the situation of the terminal Transmitting/receiving nodes may beselected and switched using a reference signal (for example, CRS,CSI-RS, or SRS) transmitted in uplink and downlink. In this case ofusing a CRS or a CSI-RS transmitted in downlink, a terminal measures CSIto each node and feeds back the CSI using uplink. Then, the base stationside determines a transmitting/receiving node on the basis of thefed-back CSI. On the other hand, in the case of using an SRS transmittedin uplink, the base station side can directly measure CSI with an SRStransmitted by the terminal. Therefore, the system using an SRS candecrease the amount of information fed-back from the terminal to thebase station in comparison with a system using a CRS or a CSI-RS.Moreover, the time required from measurement of the terminal to thecompletion of the feedback is omissible, so that a feedback delay can bereduced.

It is known that the reversibility of a channel is satisfied in TDD(Time-division duplex), and that downlink precoding, the scheduling of aPDSCH, or adaptive control is possible on the basis of the CSImeasurement result acquired using an SRS. HetNet CoMP involves a highprobability of enabling communication with a node having a small pathloss since a plurality of nodes are distributed in the cell. Therefore,it can be said that there is a high possibility of also using downlinkadaptive control using an SRS.

As described above, in and after Rel. 11 into which HetNet and CoMP areintroduced, an SRS may be used for various purposes such as not onlyuplink scheduling and adaptive control used in the related art, but alsoselection of a transmitting/receiving node and downlink adaptivecontrol.

CITATION LIST Non-Patent Literature NPL 1

-   3GPP TS 36.211 V 10.4.0, “Physical Channels and Modulation (Release    10),” December 2011

NPL 2

-   3GPP TS 36.212 V 10.4.0, “Multiplexing and channel coding (Release    10),” December 2011

NPL 3

-   3GPP TS 36.213 V 10.4.0, “Physical layer procedures (Release 10),”    December 2011

NPL 4

-   3GPP TR 36.819 v 11.1.0, “Coordinated multi-point operation for LTE    physical layer aspects,” December 2011

SUMMARY OF INVENTION Technical Problem

One or more receiving nodes for an uplink data signal are likely to beone or more receiving nodes nearest to the terminal. This is to reduceinterference with another cell or the power consumption in the terminal.On the other hand, in consideration of using an SRS for selection of atransmitting/receiving node or downlink adaptive control, an SRS isrequired to be receivable at nodes in a larger range. That is, inHetNet, an uplink data signal and an SRS are required to be receivablein different nodes.

The transmission power of an SRS is given by Equation 1. In thisequation, P_(CMAX,c)(i), P_(O) _(—) _(PUSCH,c)(j), α_(C)(j)·PL_(c), andf_(c)(i) are provided by diverting terms included in the transmissionpower equation of a PUSCH. The term of 10 log₁₀(M_(SRS,c)) is a term forproportioning the transmission power of an SRS to the transmission bandwidth, i.e., for keeping the constancy of the transmission powerdensity. This equation is different from a PUSCH only in parameterP_(SRS) _(—) _(OFFSET,c)(m) indicated from a higher layer. P_(SRS) _(—)_(OFFSET,c)(m) represents a transmission power offset given to an SRSfor uplink data (PUSCH). P_(SRS) _(—) _(OFFSET,c)(m) can be set asindependent two values according to the type of SRS (A-SRS or P-SRS).That is, different transmission power offsets can be given to an A-SRSand a P-SRS. From the above, it is found that an SRS can be set intodifferent power from that of a PUSCH using a parameter from a higherlayer. This can be used to thereby set an A-SRS or a P-SRS into largetransmission power suitable for reception in more receiving nodes thanobject nodes receiving a PUSCH. FIG. 2 illustrates an example forproviding different coverage between a PUSCH and an SRS using poweroffset P_(SRS) _(—) _(OFFSET,c)(m).

(Equation 1)

P _(SRS,c)(i)=min{P _(CMAX,c)(i),P _(SRS) _(—) _(OFFSET,c)(m)+10 log₁₀(M_(SRS,c))+P _(O) _(—) _(PUSCH,c)(j)+α_(c)(j)·PL _(c) +f _(c)(i)}  [1]

However, a power offset indicated from a higher layer does not enable afrequent high-speed transmission power control. In particular, there isa problem in that this control cannot follow the fading fluctuationcaused by movement of a terminal or a variation in a surroundingenvironmental. In LTE, a TPC command included in a control signal (DCI)for instructing data allocation is used as a system of performinghigh-speed control on transmission power of an uplink control signal(PUCCH: Physical Uplink Control Channel) or a PUSCH. TPC commands areaccumulated every time being received and are used for calculation oftransmission power. Thereby, the base station indicates transmissionpower control using a TPC command according to the situation of aterminal and can more precisely change transmission power faster thanhigher layer signaling. Hereinafter, power control through a TPC commandis referred to as closed loop TPC.

In the conventional method, a closed loop TPC for PUSCH and a closedloop TPC for a PUCCH are performed separately. More specifically, in aplurality of DCI formats, a TPC command included in DCI format 0/4indicating data assignment information on a PUSCH is used for a closedloop TPC for PUSCH, and a TPC command included in DCI formats1/1A/1B/1D/2/2A/2B/2C indicating data assignment information on a PDSCHis used for closed loop TPC for PUCCH. Hereinafter, a TPC commandaccumulation value for a PUSCH is represented with f_(c)(i), and a TPCcommand accumulation value for PUCCH is represented with g(i).

As can be seen from Equation 1, the transmission power of an SRS iscontrolled using a closed loop TPC. However, this is provided bydiverting TPC command accumulation value f_(c)(i) of a PUSCH. In otherwords, this represents that a node receiving an SRS is assumed to be thesame as a node receiving the data of a PUSCH. In conventional systems,the node receiving a PUSCH is always the same as the node receiving anSRS, an SRS is transmitted in order to measure CSI for scheduling of aPUSCH, and the assumption described above can therefore be applied foroperations. However, in Rel. 11 as described above, uplink data (PUSCH)and an SRS may be received by different nodes. In such a case, it isdesirable that transmission power control of these signals can beperformed separately using independent TPC commands.

FIG. 3 illustrates an example of a terminal receiving a PDSCH or thelike from a macro node and transmitting a PUSCH to a pico node. Thereception range (coverage) for PUSCH data has a different size from thecoverage for an SRS due to transmission power offset. In this situation,if a terminal approaches a PUSCH receiving pico node, a base stationissues an instruction for decreasing transmission power using a TPCcommand. Since the transmission power of the SRS also decreasesaccording to the TPC command, the SRS cannot be received with necessaryquality in, for example, the macro node illustrated in FIG. 3. On thecontrary, if the terminal moves away from the PUSCH receiving pico node,the base station issues an instruction for increasing transmission powerusing a TPC command. Since the transmission power of an SRS alsoincreases according to the TPC command, transmission is performed withexcessive power. An SRS with such excessive power increases interferencewith another cell to result in deterioration of CSI measurement accuracyof the SRS.

It is an object of the present invention to provide a radiocommunication terminal apparatus, a radio communication base stationapparatus, and a radio communication method that can perform a flexibletransmission power control of an SRS without restrictions due to thetransmission power control of a PUSCH, in order to enable use of an SRSfor various purposes in a HetNet CoMP environment.

Solution to Problem

A radio communication terminal apparatus according to an aspect of thepresent invention includes: a receiving section that receives a controlsignal including a TPC command to be applied to an A-SRS, through aphysical downlink control channel; a control section that updates atransmission power value of the A-SRS using the TPC command; and atransmitting section that transmits the A-SRS using the updatedtransmission power value in accordance with a transmission requestincluded in a control signal indicating assignment of a physicaldownlink data channel or assignment of a physical uplink data channel.

A radio communication base station apparatus according to an aspect ofthe present invention includes: a transmitting section that transmits acontrol signal including a TPC command to be applied to an A-SRS, and acontrol signal indicating one of assignment of a physical downlink datachannel and a physical uplink data channel through a physical downlinkcontrol channel; and a control section that determines a value of theTPC command, an A-SRS transmission request, and a transmission/receptionparticipating node based on a result of CSI measurement.

A radio communication method according to an aspect of the presentinvention includes: receiving a control signal including a TPC commandto be applied to an A-SRS, through a physical downlink control channel;updating a transmission power value of the A-SRS using the TPC command;and transmitting the A-SRS using the updated transmission power value inaccordance with a transmission request included in a control signalindicating assignment of a physical downlink data channel or assignmentof a physical uplink data channel.

Advantageous Effects of Invention

According to the present invention, a terminal can perform atransmission power control on an SRS independently of a PUSCH.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram of a HetNet CoMP cell;

FIG. 2 illustrates the reception ranges (coverage) of uplink data and anSRS;

FIG. 3 illustrates an example of performing a conventional closed loopTPC in HetNet CoMP;

FIG. 4 is a block diagram illustrating a configuration of a main portionof a macro node according to Embodiment 1 of the present invention;

FIG. 5 is a block diagram illustrating a configuration of a main portionof a pico node according to Embodiment 1 of the present invention;

FIG. 6 is a block diagram illustrating a configuration of a main portionof a terminal according to Embodiment 1 of the present invention; and

FIG. 7 illustrates the result of a transmission power control accordingto Embodiment 1 of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. In the embodiments,the same components are designated with the same reference signs, anddetailed explanations thereof will be omitted.

Embodiment 1 Configuration of Network System

A network system according to Embodiment 1 of the present invention is aHetNet or HetNet CoMP and includes macro node 100, pico node 200, andterminal (UE) 300, as illustrated in FIG. 1. One macro node 100 and oneor more pico nodes 200 are mounted in each macro cell. Pico node 200 maybe a pico base station forming its own pico cell or may be a node, suchas an RRH (Remote radio head), communicating with a terminal as a partof a distributed transmitting/receiving antenna of a macro cell. Macronode 100 and each pico node 200 are connected with an interface having alow delay and large capacity, such as an optical fiber. Macro node 100and each pico node 200 in the cell share the transmission parameter ofan SRS allocated to each terminal 300 existing in the cell, and receivethe SRS to measure CSI. Each terminal 300 communicates by radio with oneor more nodes 100 and 200 selected by macro node 100. A downlinktransmitting node and an uplink receiving node may be the same as eachother, and may be different from each other. A transmitting node and areceiving node are set individually for each terminal 300.

In the present embodiment, in addition to a conventional closed loop TPCfor a PUSCH, each terminal 300 performs a closed loop TPC for an A-SRSusing DCI format 3/3A which is a kind of control signal transmittedthrough a PDCCH in a downlink subframe.

DCI format 3/3A is a control signal enabling transmission of one controlinformation obtained by consolidating many TPC commands to one or moreterminals 300. The CRC of DCI format 3/3A is scrambled with a certain ID(RNTI), and a base station needs to beforehand indicate the RNTI to aterminal 300 in order to decode the DCI format 3/3A. In order to judgewhich one of TPC commands is a TPC command addressed to the own terminalamong terminals 300 decoding DCI format 3/3A with the same RNTI, a TPCcommand index is needed in addition to the RNTI.

Therefore, in the present embodiment, it is assumed that the basestation beforehand indicates RNTI common to terminals 300 and TPCcommand indices different between terminals 300, as individual controlinformation for the respective terminals, with an RRC control signal orthe like, to terminals 300 performing a closed loop TPC for an A-SRSusing DCI format 3/3A. Hereinafter, RNTI used for decoding DCI format3/3A for an A-SRS is referred to as TPC-SRS-RNTI. Terminal 300 notperforming a closed loop TPC with DCI format 3/3A links an A-SRS to aclosed loop TPC for a PUSCH similarly to conventional Rel. 10. In otherwords, the transmission power according to Equation 1 is used. It isassumed that a P-SRS is transmitted using the transmission poweraccording to Equation 1 similarly to conventional Rel. 10.

[Configuration of Macro Node]

FIG. 4 is a block diagram illustrating a configuration of a main portionof macro node 100 according to the present embodiment. Macro node 100illustrated in FIG. 4 mainly includes receiving section 101, measurementsection 102, inter-base station interface (IF) section 103, controlsection 104, transmitting section 105, and data determination section106. Control section 104 is not limited to be included in the macronode, and at least one control section 104 only has to be in a HetNetCoMP system connecting macro node 100 and each pico node 200.Alternatively, multiple control sections 104 may exchange informationwith each other, and any one of the control sections may also beoperated as control section 104. Hereinafter, control section 104 isassumed to be implemented as a part of macro node 100.

Receiving section 101 performs radio reception processing(down-conversion, demodulation, decode, and/or the like) on a radiosignal transmitted from each terminal 300 and received through theantenna, and extracts an SRS, a PUSCH, a PUCCH, or the like. Receivingsection 101 outputs an SRS to measurement section 102. If macro node 100is a PUSCH receiving node for terminal 300, receiving section 101outputs a PUSCH to data determination section 106.

Measurement section 102 measures CSI with an SRS and outputs themeasurement result to control section 104.

Inter-base station interface section 103 performs wired communicationwith pico node 200. More specifically, inter-base station interfacesection 103 receives the CSI measurement result transmitted from piconode 200 and forwards the result to control section 104 in macro node100. Inter-base station interface section 103 transmits informationrepresenting an instruction for participating in transmission/receptionto a transmission/reception participating node selected by controlsection 104. Inter-base station interface section 103 transmitsscheduling information on a PDSCH and a PUSCH, and a parameter necessaryfor transmitting/receiving a PDSCH and a PUSCH to and from terminal 300to pico node 200. Inter-base station interface section 103 receivesuplink data of terminal 300 forwarded from pico node 200 and outputs thedata to data determination section 106 of macro node 100.

Control section 104 controls, for example, selection of atransmission/reception participating node, scheduling and parametersetting of a PDSCH and a PUSCH, transmission power of a PUSCH and aPUCCH, and transmission power of an A-SRS. More specifically, controlsection 104 selects a transmission/reception participating node for eachterminal 300 using CSI measured from an SRS received in macro node 100and pico node 200. Control section 104 determines scheduling of a PDSCHand a PUSCH using the above CSI measurement result. Simultaneously,control section 104 determines PDSCH and PUSCH transmission/receptionparameters for each terminal 300.

Control section 104 determines the TPC command of a closed loop TPCindicated to each terminal 300. More specifically, control section 104collects the reception quality of a PUSCH or the reception quality of anSRS received in each node through inter-base station interface section103 and determines the value of a TPC command indicated at the time ofnext assignment of a PUSCH, a PUCCH and an A-SRS. Then, control section104 generates a 2-bit TPC command for indicating a transmission powercontrol of a PUSCH and includes the command in DCI format 0/4 forindicating uplink data assignment. Control section 104 generates a 1 or2-bit TPC command for indicating a transmission power control of anA-SRS and includes the command in DCI format 3/3A. Control section 104generates a 2-bit TPC command for indicating a transmission powercontrol of a PUCCH and includes the command in DCI format1/1A/1B/1D/2/2A/2B/2C for indicating downlink data assignment. Controlsection 104 generates a 1 or 2-bit transmission request command forindicating a transmission request for an A-SRS and includes the commandin DCI format 0/4 or DCI format 1A/2B/2C. Control section 104 forwardsthese DCIs to transmitting node 200 participating in transmission toterminal 300. Control section 104 outputs these DCIs to transmittingsection 105 when macro node 100 itself is a transmission participatingnode.

Transmitting section 105 generates a PDCCH, a PDSCH, or the like usingvarious DCIs received from control section 104 and data to each terminal300 and creates a downlink subframe. Then, transmitting section 105performs a transmission radio process (up-conversion or the like) on thedownlink subframe and transmits the downlink subframe to each terminal300 through the antenna.

Data determination section 106 performs channel equalization, datademodulation, data decode, and error determination using a PUSCHinputted from receiving section 101 and a PUSCH forwarded from areception participating node through inter-base station interfacesection 103. Error determination is performed using a CRC (CyclicRedundancy Check) code or the like. If there is no error, datadetermination section 106 performs next data assignment for terminal300. On the other hand, if an error is detected, data determinationsection 106 performs a retransmission control of the data for terminal300.

[Configuration of Pico Node]

FIG. 5 is a block diagram illustrating a configuration of a main portionof pico node 200 according to the present embodiment. Pico node 200illustrated in FIG. 5 mainly includes receiving section 201, measurementsection 202, inter-base station interface section 203, and transmittingsection 204.

Receiving section 201 performs radio reception processing(down-conversion and/or the like) on a radio signal transmitted fromeach terminal 300 and received through the antenna and extracts an SRS,a PUSCH, a PUCCH, or the like. Receiving section 201 outputs an SRS tomeasurement section 202. Receiving section 201 outputs the extractedPUCCH and PUSCH to inter-base station interface section 203.

Measurement section 202 measures CSI with an SRS and outputs themeasurement result to inter-base station interface section 203. Thismeasurement result is forwarded to control section 104 in macro node100.

Inter-base station interface section 203 performs wired communicationwith macro node 100. More specifically, inter-base station interfacesection 203 forwards the CSI measurement result inputted frommeasurement section 202 to macro node 100. Inter-base station interfacesection 203 receives indication information on whether correspondingpico node 200 is a transmission/reception participating node forterminal 300, from macro node 100. Inter-base station interface section203 receives scheduling information on a PDSCH and a PUSCH andparameters necessary for transmitting/receiving of a PDSCH and a PUSCH,from macro node 100. Inter-base station interface section 203 outputs aPUSCH and a PUCCH for terminal 300 received from receiving section 201to data determination section 106 in macro node 100. When pico node 200is a transmitting node, inter-base station interface section 203receives DCI generated in macro node 100 and outputs the DCI totransmitting section 204.

Transmitting section 204 generates a PDCCH, a PDSCH, and/or the likeusing various DCIs received from inter-base station interface section203 and data to each terminal 300 and creates a downlink subframe. Then,transmitting section 204 performs radio transmission processing(up-conversion and/or the like) on the downlink subframe and transmitsthe downlink subframe to each terminal 300 through the antenna.

[Configuration of Terminal]

FIG. 6 is a block diagram illustrating a configuration of a main portionof terminal 300 according to the present embodiment. Terminal 300illustrated in FIG. 6 mainly includes receiving section 301, controlsection 302, and transmitting section 303.

Receiving section 301 performs radio reception processing(down-conversion and/or the like) on a radio signal received through theantenna and extracts a PDCCH, a PDSCH, and/or the like. Then, receivingsection 301 extracts assignment information on a PDSCH and a PUSCH, anA-SRS transmission request, a TPC command for performing a closed loopTPC for PUSCH, a TPC command for performing a closed loop TPC for PUCCH,a TPC command for performing a closed loop TPC for A-SRS, or the like,from the PDCCH. Then, receiving section 301 outputs the aboveinformation to control section 302.

Control section 302 performs a closed loop TPC using the TPC commandreceived from receiving section 301. Terminal 300 receiving theindication of TPC-SRS-RNTI and a TPC command index holds TPC commandaccumulation values corresponding to a PUSCH, a PUCCH, and an A-SRS andadds newly received TPC commands to respective TPC command accumulationvalues to update the values. When a transmission request of an A-SRS ismade, control section 302 instructs transmitting section 303 to transmitan A-SRS at the next timing for enabling transmission of an A-SRS. A TPCcommand with DCI format 3/3A is applied to only an A-SRS, and a P-SRS istransmitted with the same transmission power, timing, and cycle as aconventional P-SRS.

Transmitting section 303 performs radio transmission processing(up-conversion and/or the like) on a PUSCH, a PUCCH, an SRS, and/or thelike and transmits the resultants through the antenna. Transmittingsection 303 performs radio transmission radio processing on a PUSCH, aPUCCH, an SRS and/or the like according to transmission parametersindicated from control section 302.

[Operation Flow]

Next, a main processing procedure for each apparatus according to thepresent embodiment will be explained below with reference to Step (1) toStep (4).

Step (1): Macro node 100 beforehand indicates the respective parametersets for a P-SRS and an A-SRS as higher layer control information toeach terminal 300. The parameter sets include parameters common toterminals 300 in the cell and parameters assigned individually toterminals 300 in the cell. These parameter sets are parameter setsnecessary for generating a P-SRS and an A-SRS and include parametersnecessary for identifying a base sequence, a frequency resource, a timeresource, an orthogonal resource, and/or the like. Herein, the term“frequency resource” refers to a bandwidth, a frequency position, thepresence or absence of frequency hopping, or the like; the term “timeresource” refers to the transmission cycle and subframe number of aP-SRS, a transmittable subframe number of an A-SRS, and/or the like; andthe term “orthogonal resource” refers to a Comb number, a CS (CyclicShift) number, and/or the like assigned so as to differ betweenterminals 300. These parameter sets include SRS transmission poweroffset value P_(SRS) _(—) _(OFFSET,c)(m) included in Equation 1. Here,P_(SRS) _(—) _(OFFSET,c)(m) takes two values which are a value appliedto a P-SRS and a value applied to an A-SRS. These parameter sets includeTPC-SRS-RNTI and a TPC command index. These are transmitted from atransmitting node for terminal 300.

Some parameters for an A-SRS can independently be set according to theclassification of DCI including a transmission request and the value ofa transmission request bit. More specifically, five sets of a bandwidth,a frequency position, a Comb number, a CS number, or the like can beprepared to select which one of sets involves transmission of an A-SRSin according to five formats that are DCI format 0 (transmission requestbit is “1”), DCI format 1A/2B/2C (transmission request bit is “1”) andDCI format 4 (transmission request bit is “01”), (transmission requestbit is “10”), and (transmission request bit is “11”).

Step (2): macro node 100 further indicates whether a closed loop TPC foran A-SRS is performed using DCI format 3/3A as higher layer controlinformation to each terminal 300. This may be judged according towhether TPC-SRS-RNTI is indicated and may separately be indicated ascontrol information. This may be performed using DCI format 3/3A in thecase of no indication, and a closed loop TPC may be performed using aTPC command of DCI format 0/4 in the case of no indication, similarly toconventional schemes.

Step (3): next, terminal 300 sets a P-SRS transmission resourceaccording to the parameter set for a P-SRS indicated from the basestation. Then, terminal 300 periodically transmit a P-SRS. Terminal 300receives DCI format 0/1A/2B/2C/4 transmitted from a transmitting nodefor the base station and confirms whether transmission of an A-SRS isrequested. When the transmission is requested, terminal 300 transmits anA-SRS determined according to the classification of DCI and the value ofthe transmission request bit, in an A-SRS transmittable subframe whichis set beforehand. Here, in terminal 300 not having a closed loop TPCset with DCI format 3/3A, transmission power of both SRSs is givenaccording to Equation 1. On the other hand, in terminal 300 having aclosed loop TPC set with DCI format 3/3A, transmission power of a P-SRSis given according to Equation 1, and transmission power of an A-SRS isgiven according to Equation 2. Here, h_(c)(i) included in Equation 2 isa value obtained by accumulating TPC commands for an A-SRS with DCIformat 3/3A.

(Equation 2)

P _(SRS,c)(i)=min{P _(CMAX,c)(i),P _(SRS) _(—) _(OFFSET,c)(m)+10 log₁₀(M_(SRS,c))+P _(O) _(—) _(PUSCH,c)(j)+α_(c)(j)·PL _(c) +h _(c)(i)}  [2]

In addition, h_(c)(i) may be set as h_(c)(i)=f_(c)(i) at time of settinga closed loop TPC for an A-SRS with DCI format 3/3A so as to have theinitial value at the setting time equal to f_(e)(i). Alternatively,h_(c)(i) may be set as h_(c)(i)=0 at time of setting a closed loop TPCfor an A-SRS with DCI format 3/3A so as to have the initial value at thesetting time equal to 0. In an operation of seldom updating transmissionpower parameters with an RRC control signal, power control is performeddepending on a closed loop TPC. In such a case, the values of f_(c)(i)may significantly differ from 0. Therefore, h_(c)(i)=f_(c)(i) can be setat the setting time to thereby avoid a sudden change in the transmissionpower of an A-SRS transmitted by the terminal at time of setting aclosed loop TPC with DCI format 3/3A for an A-SRS. On the other hand, anoperation of frequently updating transmission power parameters with anRRC control signal is not often dependent on a closed loop TPC. In thiscase, f_(c)(i) likely has a value around 0, and h_(c)(i)=0 can be set atthe setting time to prevent an excessive accumulation value fromremaining.

Terminal 300 receives various kinds of DCI included in a PDSCHtransmitted from a transmitting node for the base station and detects aTPC command corresponding to each of a PUSCH, a PUCCH, and an A-SRS.Then, terminal 300 performs a closed loop TPC corresponding to each of aPUSCH, a PUCCH, and an A-SRS on the basis of the TPC command.

Step (4): each base station (macro node 100 and pico node 200) receivesa PUSCH, a PUCCH, and an SRS transmitted by terminal 300. An SRS is usedfor calculation of CSI, and a PUSCH and a PUCCH are decoded and aredetermined as data and control information. Macro node 100 determines atransmission/reception participating node on the basis of the CSImeasurement result obtained by each node receiving an SRS. Macro node100 determines scheduling of a PDSCH and an adaptive control on thebasis of the CSI measurement result in a transmission participatingnode. Macro node 100 determines scheduling of a subsequent PUSCH andadaptive control on the basis of the CSI measurement result and thePUSCH reception quality in a reception participating node. Since a P-SRSis received periodically, the receiving node is monitored continuously.On the other hand, an A-SRS is transmitted only when a transmissionrequest is issued.

[Advantageous Effects]

As described above, in the present embodiment, terminal 300 can performa closed loop TPC for an A-SRS independently of a PUSCH on the basis ofa TPC command included in DCI transmitted from a transmitting node forthe base station. FIG. 7 illustrates an example of a change intransmission power control on a PUSCH and an A-SRS in the case of usingthe present embodiment. In this way, even if a variation in apropagation path caused by movement of terminal 300 or a variation in asurrounding environmental occurs, an A-SRS can be controlled so as tosatisfy desired reception power in an A-SRS receiving node. Therefore,when an A-SRS is used for determination of a transmission/receptionparticipating node, CSI measurement (used for PDSCH scheduling) in atransmitting node, or the like, appropriate transmission power of anA-SRS can be maintained.

According to the present embodiment, transmission power control on anA-SRS is performed using DCI format 3/3A. DCI format 3/3A can containmany TPC commands. Therefore, the same TPC-SRS-RNTI and TPC commandindices different between terminals 300 are indicated to multipleterminals 300 similarly performing the transmission power control on anA-SRS with DCI format 3/3A. Thereby, TPC commands for a plurality ofterminals can be simultaneously sent with one DCI format 3/3A totherefore minimize an increase in the overhead.

[Variation 1]

Embodiment 1 has been explained using the case where a closed loop TPCfor an A-SRS is performed with DCI format 3/3A. However, a closed loopTPC with DCI format 3/3A may be performed for only a specific A-SRSaccording to instructions from macro node 100. A specific A-SRS is anyone of five kinds of A-SRSs having parameter sets which are setindependently according to the classification of DCI and the value of atransmission request bit as described above.

Among DCIs including a transmission request bit, DCI format 0/4 is a DCIfor indicating uplink data allocation information, and DCI format1A/2B/2C is a DCI for indicating downlink data allocation. Since thetraffic of packet data often has burstiness, assignment of a PDSCH and aPUSCH likely to concentrate temporally. In other words,transmission/reception of DCI format 0/4 and a PUSCH ortransmission/reception of DCI format 1A/2B/2C and a PDSCH/PUCCH islikely to be performed continuously. Therefore, an A-SRS transmittedaccording to a transmission request included in DCI format 0/4 may belinked with a closed loop TPC for a PUSCH, and a closed loop TPCaccording to a TPC command for an A-SRS of DCI format 3/3A may beperformed for an A-SRS transmitted according to a transmission requestincluded in DCI format 1A/2B/2C. Thereby, when PUSCHs concentrate,transmission power is controlled with a closed loop TPC for a PUSCH, andan A-SRS can be transmitted and received with power suitable forreception in a receiving node for PUSCH. Thereby, scheduling of a PUSCHand adaptive control can be performed with high accuracy on the basis ofthe transmission/reception result of an A-SRS. On the other hand, whenPDSCHs concentrate, transmission power is controlled with a closed loopTPC of DCI format 3/3A, and an A-SRS can be transmitted and receivedwith power suitable for reception in a receiving node other than a PUSCHreceiving node. Thereby, selection of a subsequenttransmitting/receiving node, scheduling of a PDSCH, and adaptive controlcan be performed with high accuracy on the basis of thetransmission/reception result of an A-SRS.

It is represented that one of five A-SRSs is set into a closed loop TPCwith DCI format 3/3A, the other A-SRSs are set into a closed loop TPClinked with a PUSCH, this enables two kinds of closed loop TPCs withonly an A-SRS, and various operations of an SRS is enabled with an A-SRSalone without using a P-SRS. Since an A-SRS is not transmittedperiodically but is transmitted on the basis of only a transmissionrequest, this is more advantageous than a P-SRS from a viewpoint ofpower consumption reduction for a terminal and the influence ofinterference. In this way, necessary operations for an SRS in HetNetCoMP can be performed with only an A-SRS.

[Variation 2]

Although DCI format 3/3A may be transmitted using all downlinksubframes, DCI format 3/3A including a TPC command for an A-SRS may betransmitted only through a subframe or a PRB with specific time and timeinterval. Accordingly, since there is no need to attempt to decode DCIformat 3/3A in all subframes, terminal 300 can reduce a processing load.Since DCI format 3/3A of an A-SRS may be transmitted only through asubframe with specific time or time interval, base station nodes 100 and200 can reduce an overhead caused by TPC command transmission.

When DCI format 3/3A including the TPC command for an A-SRS istransmitted and received only through a subframe or a PRB with specifictime and time interval, the transmitting opportunity of a TPC command ofDCI format 3/3A decreases. However, an A-SRS for performing a closedloop TPC with DCI format 3/3A is likely to be an SRS received in a moredistant node than a receiving node for a PUSCH and having a purpose ofbeing used for selection of a transmitting/receiving node. The SRS usedfor selection of a transmitting/receiving node is not required to havehigh accuracy and a short cycle for measurement of CSI in comparisonwith an SRS used for scheduling of a PUSCH. Therefore, even if thetransmission subframe or PRB of DCI format 3/3A is restricted asdescribed above to reduce the transmitting opportunity of DCI format3/3A, the accuracy of estimating an A-SRS does not deteriorate.

[Variation 3]

Furthermore, for the CRC of DCI format 3/3A for transmitting the TPCcommand for an A-SRS, an existing ID, i.e., TPC-PUSCH-RNTI orTPC-PUCCH-RNTI may be reused instead of scrambling with TPC-SRS-RNTI.TPC-PUSCH-RNTI and TPC-PUCCH-RNTI are RNTI for using DCI format 3/3A fora PUSCH and a PUCCH (for example, see NPL 3).

When acquiring no indication of RNTI, terminal 300 cannot decode DCIformat 3/3A. In other words, when one or more terminals 300 using DCIformat 3/3A for each of a PUSCH, a PUCCH, and an A-SRS exist in thecell, at least three DCI formats 3/3A have to be transmitted.

Therefore, the number of DCI formats 3/3A transmitted per subframe canbe reduced by performing the following processing. First, TPC-PUSCH-RNTIor TPC-PUCCH-RNTI and a TPC command index are indicated to terminal 300performing a closed loop TPC for an A-SRS with DCI format 3/3A. Further,control information for indicating a TPC command, which is included inDCI format 3/3A and addressed to the own terminal, to be applied to anA-SRS is indicated to corresponding terminal 300.

Accordingly, terminal 300 performing a closed loop TPC for an A-SRSusing DCI format 3/3A can perform a closed loop TPC using DCI format3/3A having CRC scrambled with TPC-PUSCH-RNTI or TPC-PUCCH-RNTI.Therefore, since a TPC command for an A-SRS can be included in DCIformat 3/3A including a TPC command for a PUSCH or a PUCCH, the numberof DCI formats 3/3A needed for the same subframe can be decreased toreduce the overhead. In contrast to TPC-SRS-RNTI having 16 bits, controlinformation indicating a TPC command, which is included in DCI format3/3A and addressed to the own terminal, to be applied to an A-SRS can beimplemented by at least 1 bit. This can also reduce the overhead for anRRC control signal.

[Variation 4]

As described above, terminal 300 performing a closed loop TPC for anA-SRS using DCI format 3/3A uses DCI format 3/3A including a TPC commandand DCI format 0/1A/2B/2C/4 including a transmission request, as acontrol signal about an A-SRS. In Embodiment 1, whether a TPC commandfor an A-SRS addressed to the own terminal is included in DCI format3/3A may be combined with whether a transmission request for an A-SRS isissued with DCI format 0/1A/2B/2C/4 in the same subframe. Thiscombination may be used to switch between f_(c)(i) and h_(c)(i) as a TPCcommand accumulation value used for calculation of transmission power.

The base station does not perform transmission of only the TPC commandfor an A-SRS with DCI format 3/3A without DCI format 0/4/1A/2B/2C in thesame subframe to corresponding terminal 300. When transmitting a TPCcommand for an A-SRS with DCI format 3/3A, the base station alsotransmits any of the DCI simultaneously at all times.

When not detecting a transmission request for an A-SRS with any DCI butdetecting only a TPC command for an A-SRS in DCI format 3/3A in the samesubframe, terminal 300 does not accumulate but discards thecorresponding TPC command Only when detecting DCI format 0/4/1A/2B/2Caddressed to the own terminal and the TPC command for an A-SRS with DCIformat 3/3A in the same subframe, terminal 300 accumulates thecorresponding TPC command into h_(c)(i).

This can reduce a possibility that recognition of the value of h_(c)(i)is different between the base station and terminal 300. If the TPCcommand to an A-SRS with DCI format 3/3A can be transmittedindependently, the base station cannot know whether a TPC commandtransmitted by the base station is correctly detected by the terminal300. The terminal also does not know whether the TPC command iscorrectly detected and accumulated. Therefore, if the base stationperforms a transmission request for an A-SRS, the A-SRS may betransmitted with significantly different transmission power from theassumption of the base station. This raises a concern that interferencewith another cell increases. On the other hand, according to thismethod, when transmitting a TPC command for an A-SRS with DCI format3/3A to terminal 300, the base station also transmits DCI format0/4/1A/2B/2C simultaneously at all times. Additionally, only whendetecting both a TPC command for an A-SRS with DCI format 3/3A and anyof the DCI simultaneously, terminal 300 accumulates the correspondingTPC command into h_(c)(i). Therefore, when the TPC command is detectedand accumulated into h_(c)(i), terminal 300 always transmits a PUSCHinvolving control information transmitted with DCI format 0/4/1A/2B/2Cor a PUCCH corresponding to a PDSCH. According to whether a PUSCH or aPUCCH is transmitted from corresponding terminal 300, the base stationcan know whether the TPC command is accumulated into h_(c)(i).

Even in a case where a predetermined different subframe timing is setfor a TPC command for an A-SRS with DCI format 3/3A and the transmissionrequest for an A-SRS with DCI format 0/1A/2B/2C/4 instead of the samesubframe timing as described above, the equivalent advantageous effectscan be obtained.

[Variation 5]

In addition to the above explanation, when detecting the transmissionrequest for an A-SRS with any DCI in the same subframe or apredetermined subframe timing difference and not detecting the TPCcommand for an A-SRS in DCI format 3/3A, terminal 300 may transmit anA-SRS with transmission power calculated using Equation 1. That is,terminal 300 calculates transmission power using accumulation valuef_(c)(i).

This enables effective utilization of a radio resource for an A-SRSallocated to corresponding terminal 300. Equation 1 representstransmission power calculated for the purpose of reception in a PUSCHreceiving node, and Equation 2 represents transmission power calculatedso as to enabling reception even in another node. Therefore, the valueof Equation 1 has a high possibility of being smaller than that ofEquation 2. That is, an A-SRS transmitted according to Equation 1 causessmaller interference with another cell than the case of using Equation2.

When making a transmission request for an A-SRS to terminal 300, thebase station allocates a radio resource for transmitting an A-SRS tocorresponding terminal 300. Therefore, even when not detecting a TPCcommand with DCI format 3/3A, terminal 300 can transmit an A-SRS withtransmission power according to Equation 1 to thereby assign theallocated radio resource to transmission of an A-SRS. At this time,terminal 300 can also use Equation 1 for calculation of transmissionpower to reduce an increase in interference with another cell.

Embodiment 2

Embodiment 2 will be explained in the case where a closed loop TPC foran A-SRS is performed by a TPC command included in DCI format1/1A/1B/1D/2/2A/2B/2C. Here, a TPC command included in DCI format1/1A/1B/1D/2/2B/2C refers to a TPC command which is conventionallyapplied to a PUCCH and which is accumulated into g(i). It is assumedthat terminal 300 is beforehand indicated to perform a closed loop TPCfor an A-SRS with a TPC command included in DCI format1/1A/1B/1D/2/2A/2B/2C, with RRC control information or the like from thebase station. If receiving the above indications, terminal 300 replacesf_(c)(i) in the transmission power equation for an A-SRS with g(i).

A configuration of a network system according to Embodiment 2 is thesame as that of Embodiment 1. In Embodiment 2, the main configurationsof macro node 100, pico node 200, and terminal 300 are also the same asthose of Embodiment 1. In Embodiment 2, the function of control section302 of terminal 300 is different from that of Embodiment 1.

[Additional Function of Terminal]

Control section 302 of terminal 300 performs a closed loop TPC for anA-SRS using a TPC command for a PUCCH. That is, control section 302adjusts the transmission power of an A-SRS on the basis of a TPC commandincluded in received DCI format 1/1A/1B/1D/2/2B/2C. Therefore, thetransmission power of an A-SRS is given by Equation 3. In Equation 3, g(i) is the accumulation value of TPC commands included in thetransmission power equation for a PUCCH.

(Equation 3)

P _(SRS,c)(i)=min{P _(CMAX,c)(i),P _(SRS) _(—) _(OFFSET,c)(m)+10 log₁₀(M_(SRS,c))+P _(O) _(—) _(PUSCH,c)(j)+α_(c)(j)·PL _(c) +g(i)}  [3]

[Advantageous Effects]

The present embodiment can perform a closed loop TPC for an A-SRS with aTPC command for a PUCCH. A PUCCH is a control signal, does not have thefunction for a retransmission control, and therefore needs to be surelyreceived with high quality in comparison with a PUSCH. Therefore, aPUCCH is likely to be received by more receiving nodes in comparisonwith a PUSCH to thereby perform a closed loop TPC so as to acquire ahigh receiving diversity effect. Moreover, a PUCCH includes feedbackinformation on a downlink retransmission control or a transmissionadaptive control, and is therefore likely to undergo a closed loop TPCso as to be received also by a transmitting node for a PDSCH.Furthermore, in consideration of performing a retransmission control ora transmission adaptive control in control section 104 in the macronode, a PUCCH is also likely to undergo a closed loop TPC so as to beable to be received by macro node 100 regardless of the location ofterminal 300.

In order to receive PUCCHs in many nodes, PUCCHs need to be transmittedwith larger power than that of PUSCHs. A transmitting node for a PDSCHis often as distant as or more distant than a receiving node for aPUSCH, and a PUCCH needs to be transmitted with higher power than thatof a PUSCH in order to receive a PUCCH in a transmitting node for aPDSCH. Also when macro node 100 transmits a PUCCH, the PUCCH has to betransmitted with high power in comparison with a PUSCH received by anearby node. As seen from the above, it can be said that wider coverageneeds to be provided for a PUCCH than that for a PUSCH. Therefore, aclosed loop TPC for an A-SRS can be performed with a TPC command for aPUCCH to attain advantageous effects equivalent to Embodiment 1.Moreover, at this time, since it is unnecessary to use a new TPCcommand, signaling necessary for a closed loop TPC for an A-SRS does notneed to be added.

[Variation 1]

Embodiment 2 has been explained in the case where a closed loop TPC foran A-SRS is performed with a TPC command included in DCI format1/1A/1B/1D/2/2A/2B/2C. However, a closed loop TPC for only a specificA-SRS may be performed with a TPC command included in DCI format1/1A/1B/1D/2/2A/2B/2C. A specific A-SRS is any one of five kinds ofA-SRSs having parameter sets which are set independently according tothe classification of DCI and the value of a transmission request bit asdescribed above.

Thereby, a closed loop TPC for some of A-SRSs is linked with a PUSCH, aclosed loop TPC for some of A-SRSs is linked with a PUCCH, and this canform different coverage according to the classification of an A-SRS.Therefore, without using a P-SRS, various operations of an SRS can beachieved with only an A-SRS. Determining which of A-SRSs is targeted onapplying a TPC command included in DCI format 1/1A/1B/1D/2/2A/2B/2C,according to the classification of DCI and the value of a transmissionrequest bit, may be regulated beforehand, and may be indicated with RRCcontrol information or the like by the base station.

[Variation 2]

Embodiment 2 has been explained using the case where f_(c)(i) in thetransmission power equation for an A-SRS is replaced with g(i) in thecase of setting of performing a closed loop TPC for an A-SRS with a TPCcommand included in DCI format 1/1A/1B/1D/2/2A/2B/2C from the basestation. However, while f_(c)(i) is held, an accumulated TPC command maybe set as a TPC command included in DCI format 1/1A/1B/1D/2/2A/2B/2C.That is, a TPC command accumulation value is equal to f_(c)(i) when theabove setting is performed, and a TPC command as a subsequentaccumulation object may be set as a TPC command included in DCI format1/1A/1B/1D/2/2A/2B/2C.

This can avoid, in the case of switching a TPC command performing aclosed loop TPC for an A-SRS, a possibility of replacing f_(c)(i) withg(i), significantly varying transmission power between before and afterthe switching, and transmitting an A-SRS with excessive power toincrease interference with another cell, or can avoid incapability ofreception with necessary quality in a target node due to insufficientlylow power.

The embodiments of the present invention have been described thus far.

In the embodiments described above, the present invention is configuredwith hardware by way of example, but the invention may also be providedby software in concert with hardware.

In addition, the functional blocks used in the descriptions of theembodiments are typically implemented as LSI devices, which areintegrated circuits. The functional blocks may be formed as individualchips, or a part or all of the functional blocks may be integrated intoa single chip. The term “LSI” is used herein, but the terms “IC,”“system LSI,” “super LSI” or “ultra LSI” may be used as well dependingon the level of integration.

In addition, the circuit integration is not limited to LSI and may beachieved by dedicated circuitry or a general-purpose processor otherthan an LSI. After fabrication of LSI, a field programmable gate array(FPGA), which is programmable, or a reconfigurable processor whichallows reconfiguration of connections and settings of circuit cells inLSI may be used.

Should a circuit integration technology replacing LSI appear as a resultof advancements in semiconductor technology or other technologiesderived from the technology, the functional blocks could be integratedusing such a technology. Another possibility is the application ofbiotechnology and/or the like.

A radio communication terminal apparatus according to the embodimentsdescribed above includes: a receiving section that receives a controlsignal including a transmission power control command (TPC command) tobe applied to an aperiodic sounding reference signal (A-SRS), through aphysical downlink control channel (PDCCH); a control section thatupdates a transmission power value of the A-SRS using the TPC command;and a transmitting section that transmits the A-SRS using the updatedtransmission power value in accordance with a transmission requestincluded in a control signal indicating assignment of a physicaldownlink data channel (PDSCH) or assignment of a physical uplink datachannel (PUSCH).

In the radio communication terminal apparatus according to theembodiments described above, the A-SRS is an A-SRS that is transmittedwhen a combination of a classification of the control signal includingthe transmission request and a state of a transmission-request bit is aspecific combination.

In the radio communication terminal apparatus according to theembodiments described above: the TPC command is a TPC command includedin a control signal other than the control signal indicating assignmentof a PUSCH to the radio communication terminal apparatus; the controlsignal including the TPC command includes one or a plurality of TPCcommands targeting the radio communication terminal apparatus or aplurality of radio communication terminal apparatuses; and the controlsection detects a TPC command targeting an A-SRS for the radiocommunication terminal apparatus of the control section from the controlsignal and updates the transmission power value of the A-SRS using theTPC command.

In the radio communication terminal apparatus according to theembodiments described above: the control signal including the TPCcommand is a control signal including one or a plurality of TPC commandsfor one of a PUSCH and a physical uplink control channel (PUCCH) for theradio communication terminal apparatus or a plurality of radiocommunication terminal apparatuses; the control signal includes one or aplurality of TPC commands targeting the radio communication terminalapparatus or a plurality of radio communication terminal apparatuses;and the control section detects a TPC command targeting an A-SRS for theradio communication terminal apparatus of the control section from thecontrol signal and updates the transmission power value of the A-SRSusing the TPC command.

In the radio communication terminal apparatus according to theembodiments described above: two control signals including the controlsignal including the TPC command and the control signal including thetransmission request are transmitted in an identical subframe or atpredetermined subframe timings different from each other; and thecontrol section updates the transmission power value of the A-SRS onlywhen the two control signals are detected in the identical subframe orat the predetermined subframe timings different from each other.

In the radio communication terminal apparatus according to theembodiments described above, when detecting a transmission request foran A-SRS but not detecting a TPC command for the A-SRS in the identicalsubframe or at the predetermined subframe timings different from eachother, the control section calculates the transmission power value ofthe A-SRS using a TPC command accumulation value for a PUSCH.

In the radio communication terminal apparatus according to theembodiments described above: the control signal including the TPCcommand is a control signal including a TPC command for a physicaluplink control channel (PUCCH); and the control section updates thetransmission power value of the A-SRS using the TPC command for thePUCCH.

A radio communication base station apparatus according to theembodiments described above includes: a transmitting section thattransmits a control signal including a transmission power controlcommand (TPC command) to be applied to an aperiodic sounding referencesignal (A-SRS), through a physical downlink control channel (PDCCH); acontrol section that provides an instruction to update a transmissionpower value of the A-SRS using the TPC command; a control section thatmeasures channel state information (CSI) using a received A-SRS; and atransmitting section that transmits a transmission request by includingthe transmission request in a control signal indicating assignment of aphysical downlink data channel (PDSCH) or assignment of a physicaluplink data channel (PUSCH).

A radio communication method according to the embodiments describedabove includes: receiving a control signal including a transmissionpower control command (TPC command) to be applied to an aperiodicsounding reference signal (A-SRS), through a physical downlink controlchannel (PDCCH); updating a transmission power value of the A-SRS usingthe TPC command; and transmitting the A-SRS using the updatedtransmission power value in accordance with a transmission requestincluded in a control signal indicating assignment of a physicaldownlink data channel (PDSCH) or assignment of a physical uplink datachannel (PUSCH).

The disclosure of the specification, drawings, and abstract included inJapanese Patent Application No. 2012-171086, filed on Aug. 1, 2012 isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a radio communication terminalapparatus, a radio communication base station apparatus, and a radiocommunication method in a mobile communication system, for example.

REFERENCE SIGNS LIST

-   100 Macro node-   101 Receiving section-   102 Measurement section-   103 Inter-base station interface section-   104 Control section-   105 Transmitting section-   106 Data determination section-   200 Pico node-   201 Receiving section-   202 Measurement section-   203 Inter-base station interface section-   204 Transmitting section-   300 Terminal-   301 Receiving section-   302 Control section-   303 Transmitting section

1. A radio communication terminal apparatus comprising: a receivingsection that receives a control signal including a transmission powercontrol command (TPC command) to be applied to an aperiodic soundingreference signal (A-SRS), through a physical downlink control channel(PDCCH); a control section that updates a transmission power value ofthe A-SRS using the TPC command; and a transmitting section thattransmits the A-SRS using the updated transmission power value inaccordance with a transmission request included in a control signalindicating assignment of a physical downlink data channel (PDSCH) orassignment of a physical uplink data channel (PUSCH).
 2. The radiocommunication terminal apparatus according to claim 1, wherein the A-SRSis an A-SRS that is transmitted when a combination of a classificationof the control signal including the transmission request and a state ofa transmission-request bit is a specific combination.
 3. The radiocommunication terminal apparatus according to claim 1, wherein: the TPCcommand is a TPC command included in a control signal other than thecontrol signal indicating assignment of a PUSCH to the radiocommunication terminal apparatus; the control signal including the TPCcommand includes one or a plurality of TPC commands targeting the radiocommunication terminal apparatus or a plurality of radio communicationterminal apparatuses; and the control section detects a TPC commandtargeting an A-SRS for the radio communication terminal apparatus fromthe control signal and updates the transmission power value of the A-SRSusing the TPC command.
 4. The radio communication terminal apparatusaccording to claim 2, wherein: the control signal including the TPCcommand is a control signal including one or a plurality of TPC commandsfor one of a PUSCH and a physical uplink control channel (PUCCH) for theradio communication terminal apparatus or a plurality of radiocommunication terminal apparatuses; the control signal includes one or aplurality of TPC commands targeting the radio communication terminalapparatus or the plurality of radio communication terminal apparatuses;and the control section detects a TPC command targeting an A-SRS for theradio communication terminal apparatus from the control signal andupdates the transmission power value of the A-SRS using the TPC command.5. The radio communication terminal apparatus according to claim 3,wherein: two control signals including the control signal including theTPC command and the control signal including the transmission requestare transmitted in an identical subframe or at predetermined subframetimings different from each other; and the control section updates thetransmission power value of the A-SRS only when the two control signalsare detected in the identical subframe or at the predetermined subframetimings different from each other.
 6. The radio communication terminalapparatus according to claim 5, wherein when detecting a transmissionrequest for an A-SRS but not detecting a TPC command for the A-SRS inthe identical subframe or at the predetermined subframe timingsdifferent from each other, the control section calculates thetransmission power value of the A-SRS using a TPC command accumulationvalue for a PUSCH.
 7. The radio communication terminal apparatusaccording to claim 1, wherein: the control signal including the TPCcommand is a control signal including a TPC command for a physicaluplink control channel (PUCCH); and the control section updates thetransmission power value of the A-SRS using the TPC command for thePUCCH.
 8. A radio communication base station apparatus comprising: atransmitting section that transmits a control signal including atransmission power control command (TPC command) to be applied to anaperiodic sounding reference signal (A-SRS), through a physical downlinkcontrol channel (PDCCH); a control section that provides an instructionto update a transmission power value of the A-SRS using the TPC command;a measurement section that measures channel state information (CSI)using a received A-SRS; and a transmitting section that transmits atransmission request by including the transmission request in a controlsignal indicating assignment of a physical downlink data channel (PDSCH)or assignment of a physical uplink data channel (PUSCH).
 9. A radiocommunication method comprising: receiving a control signal including atransmission power control command (TPC command) to be applied to anaperiodic sounding reference signal (A-SRS), through a physical downlinkcontrol channel (PDCCH); updating a transmission power value of theA-SRS using the TPC command; and transmitting the A-SRS using theupdated transmission power value in accordance with a transmissionrequest included in a control signal indicating assignment of a physicaldownlink data channel (PDSCH) or assignment of a physical uplink datachannel (PUSCH).